Fair Value Measurements - Assets and Liabilities Measured at Fair Value on a Non-Recurring Basis (Detail) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2015		Dec. 31, 2014
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Other real estate	$ 7,033		$ 7,298
Fair Value, Measurements, Nonrecurring [Member] | Models with Significant Unobservable Market Parameters (Level 3) [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Other real estate	7,033		7,298
Impaired loans, net	10,795	[1]	8,866	[1]
Total	17,828		16,164
Fair Value, Measurements, Nonrecurring [Member] | Reported Value Measurement [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Other real estate	7,033		7,298
Impaired loans, net	10,795	[1]	8,866	[1]
Total	$ 17,828		$ 16,164

[1] Amount is net of a valuation allowance of $1.4 million at March 31, 2015 and $1.6 million at December 31, 2014 as required by ASC 310, "Receivables."